G80S Loss of Power with Throttle Opening
Posted: Tue Oct 01, 2019 6:41 pm
Hello all,
This is my first post having been gifted a 1956 G80S by my wife for my 30th Birthday back in May.
The bike generally runs well and starts fine. It has had a bottom end rebuild fairly recently and I am slowly running it in.
I have one issue that i would appreciate some guidance with on as i haven't worked much on this bike and most of my experience is with two stroke trials bikes.
If I am cruising at around 60 mph in top gear, all is well and can be comfortably sustained, but if I open the throttle beyond a point (around 1/3 throttle) it seems that the engine loses all power almost instantly. It felt like the engine was seizing or perhaps overheating the first time I experienced it, but closing the throttle progressively back to around 1/3 throttle almost immediately restores normal operation again so I suspect carburation.
My first thought was a fuel flow issue but I am surprised, if this is the case, that i have not experienced it when climbing sustained gradients or from similar throttle demands in lower gears and the issue is not progressive like when the fuel needs switching to reserve. I suspect that carburation may be a bit rich as friends who follow comment on a more strong smell of petrol than is normal even for this era of bike.
Any advice for setting the carb up properly would be appreciated before I start, or more importantly, if there are any other culprits to check as i am surprised that a carburation issue would not be more progressive with misfiring rather than a total loss of power.
Is there a recommended way of setting up the float height and getting the main needle height correct?
Advice gratefully received.
Kind regards,
Bob
This is my first post having been gifted a 1956 G80S by my wife for my 30th Birthday back in May.
The bike generally runs well and starts fine. It has had a bottom end rebuild fairly recently and I am slowly running it in.
I have one issue that i would appreciate some guidance with on as i haven't worked much on this bike and most of my experience is with two stroke trials bikes.
If I am cruising at around 60 mph in top gear, all is well and can be comfortably sustained, but if I open the throttle beyond a point (around 1/3 throttle) it seems that the engine loses all power almost instantly. It felt like the engine was seizing or perhaps overheating the first time I experienced it, but closing the throttle progressively back to around 1/3 throttle almost immediately restores normal operation again so I suspect carburation.
My first thought was a fuel flow issue but I am surprised, if this is the case, that i have not experienced it when climbing sustained gradients or from similar throttle demands in lower gears and the issue is not progressive like when the fuel needs switching to reserve. I suspect that carburation may be a bit rich as friends who follow comment on a more strong smell of petrol than is normal even for this era of bike.
Any advice for setting the carb up properly would be appreciated before I start, or more importantly, if there are any other culprits to check as i am surprised that a carburation issue would not be more progressive with misfiring rather than a total loss of power.
Is there a recommended way of setting up the float height and getting the main needle height correct?
Advice gratefully received.
Kind regards,
Bob